1. Field of the Invention
The present invention relates generally to laboratory flasks. More particularly the present invention relates to improvements in flasks for growing cells, microorganisms and tissue in a culture medium.
2. Description of the Related Art
Tissue culture flasks are widely used in the laboratory for many purposes. Typically, these flasks are used to culture microorganisms or tissues in a culture medium or agar which is adhered to an interior surface of the flask. The tissues are introduced into the flask through a capped opening. The flask is re-capped and inserted into a stacking facility or chamber, such as an oven, to facilitate the growth of the microorganisms in the medium. In laboratory practice, it is quite common to arrange or stack several tissue culture flasks in a single chamber. Thus, the size of the individual flasks becomes a concern as it is desirable to position as many flasks as possible in a single chamber.
Another concern in constructing tissue culture flasks is the volume within the flask which is available for accommodation of both the culture medium as well as the tissue. In order to enhance stackability of the flasks in the chamber, many tissue culture flasks are generally flat rectangular containers having a neck or opening at one end wall permitting access to the interior of the flask. The flask may be filled with culture medium and tissue to a level approaching the bottom of the neck or opening. Thus, the usable volume of the flask is determined by the vertical distance between the bottom wall of the flask and the flask opening, since the culture medium and tissue cannot extend above the flask opening. Spacing the opening from the bottom wall of the flask increases the usable volume of the flask, but also increases the overall stacked height of the flask. Thus, fewer flasks can be stacked in a chamber. The size of the opening of the flask can be decreased to increase the usable volume. However, a smaller opening limits accessibility to the entire bottom wall of the flask. This reduced accessibility creates problems, particularly in those situations where it is necessary to access the tissue growing in the medium on the bottom wall of the flask. An optimal flask would permit the user to access the entire bottom surface of the flask, including the corners, with a scraper, pipette or other instrument.
It is therefore desirable to provide a tissue culture flask having a sufficiently large opening so as to permit access to the entire bottom surface thereof without decreasing the usable volume or increasing the stacked height of the flask.
It is another object of the present invention to provide an improved laboratory flask for the culturing of microorganisms, cells and tissues.
It is a further object of the present invention to provide a tissue culture flask which permits access to the interior of the flask through an opening therein.
It is still a further object of the present invention to provide a tissue culture flask of minimal stacked height which maximizes the usable volume for culture medium and tissue.
The invention is a laboratory flask including a planar bottom wall and a planar ramp extending up from the bottom wall. The ramp defines an acute angle incline with respect to the planar bottom wall. The flask further includes a plurality of interconnected sidewalls extending up from the bottom wall and the ramp for defining an enclosure about the bottom wall and the ramp. The sidewalls preferably are aligned substantially perpendicular to the plane of the bottom wall. A top wall or cover extends across portions of the sidewalls remote from the bottom wall and the ramp. The top wall is substantially planar and substantially parallel to the bottom wall to facilitate stacking of a plurality of flasks.
Access to the interior of the flask is achieved by an elongate hollow neck that projects from a sidewall that intersects an area of the ramp furthest from the planar bottom wall. The hollow neck has a central axis aligned at an acute angle to the bottom wall, and preferably at an acute angle that is less than the angle between the ramp and the bottom wall. Exterior portions of the hollow neck may be substantially cylindrical at locations spaced from the sidewalls and may have an array of external threads at the end of the neck spaced from the sidewalls of the flask.
The interior of the hollow neck is not uniformly cylindrical along the length of the neck. More particularly, the interior of the neck may be cylindrical with a substantially constant internal diameter at locations adjacent the threaded end of the neck. However, a slight tapering consistent with molding techniques may be required. Interior portions of the neck adjacent the sidewalls of the flask are not cylindrical, and define a combination of a circular and elliptical sections at the opening adjacent the sidewall. In particular, the upper half of the opening adjacent the sidewall of the neck may be generally circularly generated. However, the lower half of the interior of the hollow neck adjacent the sidewall are generally elliptical, with the major axis of the ellipse being substantially parallel to the bottom wall. The elliptical bottom half of the interior of the neck adjacent the sidewall of the flask may be substantially tangent to the planar ramp.
Interior portions of the hollow neck then gradually change in cross-section between the externally threaded end of the neck and the opening in the sidewall that communicates with the interior of the flask. In view of this geometry, a line extending along the low points of the interior of the hollow neck defines an angle with respect to the planar bottom wall that is less than the angle defined by both the ramp and the central axis of the hollow neck. The geometry of the interior of the hollow neck relative to the ramp and the bottom wall ensures that the neck opening is above the media level and reduces the risk of contamination in the flask. Additionally, the geometry of the interior of the neck allows for sufficient and efficient access by pipettes, scraper or other instruments.